Okay, I know you'll probably all think I'm dense but it just hit me how the fact of all my seams being a bit deeper than 1/4" is probably my exact problem. That last strip is always a tad longer than the rest of the pieced block. I was thinking the problem was with that last strip itself. Thinking my 1/4" seam was too scant or something on that last strip (like I was sewing different on that last strip, huh? :P). Anyways, I know many of you have said you think the problem is my 1/4" being too deep, but I just couldn't see how that was causing this, until now! I can't explain how I see it in my mind but I totally understand it. I'm going to work on my scant 1/4" and try with the next block to see if that doesn't go a long ways in helping. I've really appreciated all the pinning and basting tips too! Besides just throwing a pin in here and there, and nesting seams, I've never known any better methods.
Thanks sooooo much again everyone! This board has helped me in so many ways thus far to improve my quilting, and I know y'all will continue to help me in the future!